/Engine/Source/Editor/KismetCompiler/Public/KismetCompiler.h
This function maps the nodes in the execution path through the expansion and back to the outer tunnel instance node. If Blueprint debugging is enabled, this function also spawns one or more intermediate "boundary" NOPs around the tunnel I/O pair. The boundary nodes are intended to serve as debug sites, allowing breakpoints to be hit on both sides of the tunnel.
void ProcessIntermediateTunnelBoundary ( [UK2Node_Tunnel](API\Editor\BlueprintGraph\UK2Node_Tunnel) * TunnelInput, [UK2Node_Tunnel](API\Editor\BlueprintGraph\UK2Node_Tunnel) * TunnelOutput )